Abstract : An investigation is reported of a unique castable carbon material developed for rocket nozzle applications. The second and third subscale nozzles (for the 5,000 pound thrust motor) were motor tested at the Air Force Rocket Propulsion Laboratory. In the second subscale test, the exit cone was burned off the nozzle after 43 seconds following excessive erosion of the cast carbon immediately aft of the graphite throat insert. The third subscale nozzle, which consisted entirely of cast carbon in a steel housing, performed acceptably. Throat performance was good but uneven erosion aft of the throat produced local gouging in the exit cone. Emphasis will be placed on improved material for the throat and initial expansion area. (Author)